Immunoassay based on surface plasmon oscillations.

An in situ immunoassay technique is described which is sensitive to specific binding to surface immobile antigen or antibody. The phenomena of surface plasmon oscillations are shown to be sensitive to antigen-antibody binding on a substrate. An advantage of the technique is that no molecular labeling is required. The technique allows the detection of the presence of approximately 6 X 10(8) molecules on the approximately 1 mm2 area of detection (approximately 1.5 X 10(-8) g/cm2). An elementary apparatus is described which allows the kinetics of the antigen-antibody binding to be accurately recorded in real time. A detailed example is presented. A second version of the apparatus of similar accuracy with improved temporal resolution is described.